| Career - ERA | |||
| Rk | Player Name | Totals | |
| 1 | Randy Johnson | 2.77 | |
| 2 | Mike Morgan | 2.77 | |
| 3 | DENNIS MARTINEZ | 2.91 | |
| 4 | Corey Kluber | 3.49 | |
| 5 | Ken Hill | 3.54 | |
| 6 | Chris Carpenter | 3.59 | |
| 7 | Roy Halladay | 3.62 | |
| 8 | Pete Harnisch | 3.87 | |
| 9 | Brad Radke | 3.95 | |
| 10 | Dustin Hermanson | 4.08 | |
| 11 | Javier Vazquez | 4.22 | |
| 12 | John Smiley | 4.23 | |
| 13 | Yu Darvish | 4.29 | |
| 14 | Andy Ashby | 4.62 | |
| 15 | Jake Peavy | 4.63 | |
| 16 | Martin Perez | 4.75 | |
| 17 | Matt Garza | 4.92 | |
| 18 | Daniel Norris | 4.94 | |
| 19 | Edwin Jackson | 4.95 | |
| 20 | Garrett Richards | 4.99 | |
| 21 | Joey Hamilton | 5.00 | |
| 22 | Shohei Ohtani | 5.10 | |
| 23 | Darryl Kile | 5.16 | |
| 24 | Jaime Garcia | 5.21 | |
| 25 | Bud Norris | 5.55 | |
| Single Season - ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Mike Morgan | 1.49 | 1993 | ||
| 2 | DENNIS MARTINEZ | 2.02 | 1993 | ||
| 3 | Ken Hill | 2.16 | 1993 | ||
| 4 | Randy Johnson | 2.21 | 1996 | ||
| 5 | Chris Carpenter | 2.62 | 2006 | ||
| 6 | DENNIS MARTINEZ | 2.70 | 1992 | ||
| 7 | Mike Morgan | 2.78 | 1992 | ||
| 8 | Randy Johnson | 2.86 | 1993 | ||
| 9 | Pete Harnisch | 2.89 | 1993 | ||
| 10 | Pedro Martinez | 2.96 | 2004 | ||
| 11 | Corey Kluber | 2.97 | 2015 | ||
| 12 | Roy Halladay | 3.02 | 2006 | ||
| 13 | Randy Johnson | 3.05 | 1994 | ||
| 14 | Nathan Eovaldi | 3.06 | 2024 | ||
| 15 | Dan Haren | 3.11 | 2009 | ||
| 16 | John Smiley | 3.21 | 1997 | ||
| 17 | Jose Contreras | 3.30 | 2010 | ||
| 18 | Dave Mlicki | 3.32 | 1998 | ||
| 19 | Ken Hill | 3.32 | 1992 | ||
| 20 | Javier Vazquez | 3.33 | 2004 | ||
| 21 | Corey Kluber | 3.35 | 2017 | ||
| 22 | Randy Johnson | 3.36 | 1995 | ||
| 23 | Roy Halladay | 3.42 | 2004 | ||
| 24 | Yu Darvish | 3.47 | 2021 | ||
| 25 | Roy Halladay | 3.56 | 2002 | ||